The first words of the novel, “Happy families are all alike; every unhappy family is unhappy in its own way “ can be alternatively interpreted as an attention-catcher, a banality, or a plainly wrong statement of the writer whose life does not fulfill his ideals.
However, based on the assumption that the work of a genius touches us to the core because it itself touches on the ideas which serve as a foundation of the world, we can interpret it as complete and absolute truth. Accordingly, it should be read as, “(Seemingly) happy families are all alike; every unhappy family (author trying to resolve the question in a real, deep, way) is unhappy in its own way (requires an individual approach, which can be worked out only through sufferings required to obtain knowledge)”. Don't get scared, not necessarily physical suffering, but in the sense of "more wisdom - more sorrow; more knowledge - more grief."
Every person can give an obvious answer about what is right and what is wrong. Anna is her husband's wife, given to him by God, and it should stay that way. This is wrong, however, too obvious to be true. Every time a person brings in God to support his stance against others, he is prejudiced and is therefore wrong.
Vronsky is obviously Anna's true love, and true partner, if only because they are indeed lovers. The conflict here, one might say, is that Vronsky has not completed his correction, he is not perfect, whereas Anna is. The only reason she is reincarnated is for him – and he blows this chance, probably again and again.
Tolstoy is probing the veracity of this answer from many points of view, represented by the others in the novel. Will he get it? Let's wait for the next 50 pages.
Art: Heinrich Matvejevich Maniser - Anna Karenina